[BenWA]

I may have crudely found my 7YA tube as bad.

I found the pin out of it online from several sources:
http://tdsl.duncanamps.com/show.php?des=7Y4
http://www.mif.pg.gda.pl/homepages/frank.../7/7Y4.pdf
http://tdsl.duncanamps.com/link.php?target=F7255F82

As I understand it, 1+8 should have continuity, 3+6 should also, and 7 should be isolated(?). However, with my good multimeter with audible alarm continuity setting; 1+8 connect to 3+6 and to 7. All 5 pins are connected to each other inside the tube.

I found a topic over on AntiqueRadios.com where someone had the same problem ad came the same conclusion on the same tube:

I found a short between pin 7 and 1/8. I checked a 7y4 tube I had laying around it showed continuity between 1 and 8 but not 1/8 to 7. So the 7Z4 tube is shorted. It was a NOS tube from a local shop. My previous (original tube) became shorted also.

A comment from someone else states:

If you are able to measure continuity from pin 7 of a 7Y4 to pins 1 or 8, it is definitely time for a new tube.

I'm still gonna take my tubes to the guy for testing tomorrow.

The thread I am quoting from: http://www.antiqueradios.com/forums/view...6&t=175997

Further reading I have done, I see that some people wire in a fuse to protect the transformer in case of a rectifier tube failure. This sounds like a very good idea to me. Had I been out of the apartment to go check the mail when the tube died instead of being right there with it checking for voltage, I might have come back to the apartment on fire from this!

I am definitely interested in wiring in a fuse folder to protect it from catching fire.